Tuberculosis is an infection caused by the organism mycobacterium tuberculosis. The infection can spread throughout the body but is more common in the lungs. Tuberculosis is uncommon in western nations. It is more common in those who are immunocompromised, such as patients with AIDS.
There is a primary infection with tuberculosis which is often asymptomatic or has minor symptoms. Most patients mount an appropriate immune response while a small percentage go on to disseminated infection.
The findings in primary tuberculosis on chest X-ray can be anywhere in the lungs and look like other infections with white patches or consolidation. There can be lymph nodes which are enlarged in the chest and fluid collections called effusions. Eventually, the body mounts an immune response and you can get a tuberculoma which calcifies. This is a walled off infection by the body. The lymph nodes calcify as well, more common in kids.
Post primary tuberculosis
Post primary tuberculosis is a reactivation of infection, often when the immune system weakens. This can occur years later. Patients often present with cough, constitutional symptoms and blood tinged cough. Military TB can occur which is disseminated infection throughout the body. This is most easily imaged in the chest.
The abnormality in post primary tuberculosis most commonly occurs in the superior posterior (upper back part) lung in the upper or lower lobes. There are white patches (consolidation) or spots (nodules). The infection can cavitate which means that air forms inside.
Infection can spread along small airways resulting in what we call a tree in bud appearance. There can be enlarged lymph nodes. Tuberculomas can form can form which look like masses. There can be spread throughout the lungs and body called military TB. Fluid collections can occur when TB involves the pleura or coverings of the lungs.
Treatment and complications
Treatment consists of long courses of antibiotics for the given strain of tuberculosis. Patients should be assumed to be contagious until sputum analysis is done. Complications can include superimposed infections of cavities with fungal infection (aspergillosis). Infected fluid around the lungs (tuberculosis empyemas). Arteries can get damaged (pseudoaneurysms). There can be scarring and dilated airways (bronchiectasis).
Tuberculosis is an uncommon but serious infection. It can be contagious and lead to significant complications and even death. Early recognition is important. Imaging findings detailed above can be non specific and look like other infections. In some cases, characteristic findings can be seen which can give us clues to the presence of tuberculosis.